About this replacement
Wiko Ozzy / Ozzy Double Sim — 3.7V Li-ion Replacement Battery (OZZY)
This 3.7V, 1400mAh Li-ion cell replaces the original battery in the Wiko Ozzy and Ozzy Double Sim smartphones. It fits both single and dual-SIM variants, which share the same battery bay dimensions and connector. Capacity is rated at 5.18Wh, matching the factory specification.
- Ozzy and Ozzy Double Sim compatibility: Both variants use an identical 65.10 × 44.00 × 4.50mm cell with the same three-contact connector and BMS handshake protocol. The dual-SIM model draws slightly higher idle current from the second radio, but both operate within the same voltage rail and charge termination threshold.
- Bench tested on actual hardware: We ran this cell through charge-discharge cycles on the Ozzy platform. The BMS correctly reported cell state to the phone's charge IC, and termination voltage held steady at 4.2V with no false cutoff events observed.
- Fuel gauge recalibration on first use: On first installation, disable fast charging if available and run one full discharge-charge cycle before normal use. This allows the fuel gauge IC to map the new cell's discharge curve before it begins tracking state-of-charge against an uncalibrated baseline.
Why the Ozzy reports wrong battery percentage after a cell swap
The Ozzy's fuel gauge IC stores a learned discharge curve from the original cell. After installing a new cell, the IC has no reference data, so percentage readings can be inaccurate — sometimes showing 100% while the phone is nearly flat, or dropping suddenly. One full discharge to automatic shutdown followed by an uninterrupted charge to 100% forces the coulomb counter to relearn the new cell's actual capacity curve. After that single cycle, percentage readings stabilise. Do not interrupt the first charge cycle early.
Sudden shutdown at 20–30% on the replacement cell
This happens when the modem or display triggers a current spike the cell cannot sustain while maintaining voltage above the BMS cutoff threshold. The BMS reads the voltage dip as a critically low cell and disconnects before the displayed percentage reaches zero. It is not a faulty battery — it is an uncalibrated fuel gauge misreading remaining capacity. Run two full discharge-charge cycles and the cutoff point will shift back toward the correct low-voltage threshold, typically around 3.4V under load.